1. Field of the Invention
The present invention relates generally to bats for use in baseball and softball and specifically to bats with modified restitution characteristics to meet performance standards imposed by various sanctioning bodies.
2. Background of Related Art
Conventionally, bat manufacturers have endeavored to improve the performance of bats. In the case of a bat, improved performance can come in the form of, among other things, improved accuracy, reduced vibration, or increased coefficient of restitution. The latter, coefficient of restitution, relates to the power the bat imparts to the ball. In other words, the higher the coefficient of restitution of a bat, the faster the ball will rebound off the bat relative to the pitch speed.
Conventionally, bats were made out of hardwoods such as, for example, maple, birch, and ash. These woods provide good durability and reasonable cost of manufacture. In this case, however, the restitution characteristics of the bat are largely dictated (and limited) by the wood chosen. This limitation of the restitution, and thus power, of the bat, along with a certain amount of nostalgia, explains the use of wooden bats in Major League Baseball. It is thought that the extreme amount of energy major league players could impart to the ball, if armed with the more powerful aluminum or composite bats, would pose a danger to themselves, other players, and fans.
Until recently, the increased power provided by non-wooden bats was not thought to be an issue at lower levels, such as collegiate baseball and softball. As a result, aluminum and composite bats were used an unregulated in NCAA sports until approximately 1998. As a result, the materials and designs were chosen to maximize the restitution of the bat. In other words, the bats were designed to increase the velocity of the ball as it left the bat, or to be “hotter.”
As shown in FIG. 1, an example of a bat design intended to maximize restitution is shown in U.S. Pat. No. 6,872,156 to Ogawa et al. This bat 100 comprises an aluminum core 105 with tapers 110a, 110b at both ends of the barrel. The tapered portion is then wrapped with a thermal polyurethane (TPU) sheet 115 to improve the restitution properties (i.e., the power) of the bat. Unfortunately, the double taper 110a, 110b of this bat proves to be difficult using conventional aluminum manufacturing techniques (i.e., this shape cannot be swaged or extruded). In addition, the dual taper 110a, 110b requires that the TPU sleeve 115 be molded or rolled onto the bat using hot forming techniques, producing a seam 120. As a result, it is difficult to maintain the density of the material 115 during application and the seam 120 presents a possible failure point that reduces durability.
After a marked increase in hitting statistics and player injuries, however, in 1998 the NCAA began to look into regulating the bats. Initially, the bats were regulated based on the return speed of a pitch based on the swing speed of the bat. This measurement was later found to be insufficient because, unlike solid wooden bats, the balance point of hollow non-wooden bats can be manipulated to increase swing speed. The closer the balance point of the bat is to the handle, for example, the faster a player can swing the bat, which is directly related to the ball speed coming off the bat.
Since 1998, continual refinement of the NCAA standard has resulted in a rule that governs many physical aspects of bats for use in NCAA sports. The size and weight of the bat is regulated, for example, along with the moment of inertia and the Baseball Coefficient of Restitution (BBCOR). Bats must be tested in NCAA laboratories for initial certification and may be subjected to random field-testing. The latter to ensure that certain bats, such as composite bats (that tend to get “hotter” with use), remain within guidelines. Other domestic and foreign sanctioning bodies have, or are in the process of, imposing similar performance standards.
What is needed, therefore, is a bat designed, not to maximize absolute performance, but to maximize performance within a given set of guidelines. The bat should be tunable to meet different standards and inexpensive to manufacture. It is to such a bat that embodiments of the present invention are primarily directed.